Scorching seas

Research suggests marine heatwaves have become 34% more likely over the past century, with rising global temperatures likely playing a key role in the increase.

In 2011, Shark Bay – a world heritage area in Western Australia famous for its seagrass meadows and unique wildlife – faced an unprecedented marine heatwave. For more than two months, coastal water temperatures soared to 2-4C above average, damaging around 36% of the region’s seagrass meadows. In some regions, almost 90% of seagrasses died.

The extreme heat also killed vast numbers of fish, including commercial populations of scallops and crabs.

The new research, published in Current Biology, explores how this ecological turmoil could have affected a species near the top of the food chain: the bottlenose dolphin.

From 2007-17, researchers monitored groups of dolphins living across a 1,500km area in the bay. The scientists took photographs of each dolphin, allowing them to be identified by their markings and the shape of their fins.

These continuous observations allowed the researchers to keep track of population numbers and the number of new calves being born – both before and after the 2011 event.